Selective drive hub



Oct 6, 1959 J. R. sTRlcKLAND ETAL 2,907,432

SELECTIVE DRIVE HUB Filed Sept. 30, 1957 INVEN TOR. JERoME R. STR/cK/ AND ATTORNEY United States Patent 2,907,432 sELEcTIvE DRIVE HUBApplication September 30, 1957, Serial No. 687,208

"11 Claims. (Cl. 192-71) 'This invention relates to selective drive hubsfor fourwlieel drive vehicles and is directed to subject matter :similarto that of the copending application of Requa et al. Serial `Number515,994 now U.S. Patent No. 2,846,039 that has a common co-inventor.

Theforegoing copending application discloses a selec- 'tive drive hubfor four-wheel drive vehicles that includes :a plurality of radiallymovable cam-actuated pawls which move in and out of engagement with asplined member carried by the axle to produce a driving connection be-:tween the front wheels and transmission. It has now 'been determined,however, that the earlier hub design possessed certain inherentweaknesses that should be :eliminated to improve the overall utility andfunctiona- .bility of the unit. l

One of the most important of these disadvantages was the problem ofplacing the disengaged mating elements in .the aligned position whereinengagement thereof would 'take place. An improvement to overcome thisobjection- .'able feature forms 4the subject matter of the copending:applications of James R. Lloyd, Sr., Serial Number 608,766 and FrancoisA. Heck, Serial Number 678,338. Both of these applications relate tonormally-operatedand externally located devices for accomplishingrotational movement of the axle and the associated splined sleeverelative to the toothed pawls when the vehicle is at rest until theopposed teeth are aligned for engagement. It has now been found inaccordance with the teaching of the instant invention that manualrelative rotation between the mating elements of the hub is unnecessary;but, that movement of the vehicle can be used to position and engage theinterlocking members in driving relation.

A second, and no less important, problem was in the design andfabrication of the paw'ls. In one of the constructions disclosed in theRequa et al application identilied above, each pawl included a pluralityof arcuately arranged teeth which had to mate with an externally splinedsleeve upon radial movement of the pawl. The arcuate configuration ofthe mating elements coupled with the frelative radial movementtherebetween required teeth on the pawl of special design that had to befabricated with highly specialized and expensive techniques, and` frommetals of a type `not particularly noted for structural Vstrength underthe stresses to which these parts are occasionally subjected. As aresult, the pawls were found to be quite costly and to break orotherwise fail Vunder conditions of excessive loading. The presentconstruction,

on the other hand, is designed with pawls thatare quite inexpensive, canbe formed with conventional machining techniques, do not require lclosetolerances, and can be `made from metals able to withstand loads far inexcess 1foff the cam necessitated double cam surfaces which invedadditional expense in fabrication.

i u, `1F"t1ally,'the overall design oftlie Requa et al basic hubPatented Oct. 6, 1959 ICC and the improved hubs of Lloyd and Heck wassuch that many parts were required, several of which were diticult andexpensive to manufacture, also, close tolerances had to be maintained inthe mating elements which, in addition to increased direct costs,brought about higher indirect costs due to a more involved andtime-consuming assembly. The present hub eliminates these last-mentionedproblems through the use of low-cost materials, common fabricationmethods and the rapid assembly which is possible with loose-fittingparts.

This, therefore, is the principal object of the presen-t invention toprovide an improved and simplified selective drive hub for four-wheeldrive vehicles. i

A second object is to' provide a selective drive hub having avsi'mplepawl and notch interlocking arrangement that eliminates the need formating teeth.

A third object is the provision of a pawl for use in selective drivehubs that is rugged, strong, easy and inexpensive to fabricate, and one`thatl does not require the maintenance of tolerances beyond thatattainable with common machining operations.

Another object of the invention is the provision of a selective drivemember in `which the interlocking elements are automatically positionedand engaged in driving relation by movement` of the vehicle thuseliminating the need for manual relative rotation in order to align themating parts prior to forming an operative coupling therebetween. s

Still another object is to provide a hub for selectively connecting thefront wheels of a vehicle in four-wheel drive relation that Vincludes asimplified cam operator that functions to move the pawls between engagedanddisengaged positions, and springs which automatically operate toengage the pawls in driving relation upon release of the cam operator assoon as the vehicle is moved a short distance. Y

An additional object of the invention is the provision of means forselectively connecting a front wheel and a front drive axle in drivingrelation that includes radially movable pawls subject only to shearingstresses in driving relation. l

Further objects are to provide a selective drive hub which is simple andinexpensive to manufacture, assemble, service and repair; one that iscompact, lightweight pointed out specifically hereinafter in connectionwith the.

description of the drawing that follows, in which:

Figure l is a fragmentary diametrical section showing the selectivedrive hub of the present invention attached in place to the hub of afront Wheel with the front drive axle disengaged therefrom;

Figure 2 is a front elevation of the hub, portions of the face platehaving been broken away to expose the stop arrangement by which themovement of the cam operator are limited;

Figure 3 is a section taken along line 3--3 of Figure l; and,

Figure 4 is a fragmentary section taken along line 4--4 of Figure 3showing a pawl, and a radial pawl receiving slot and annular cam groovein the drive llange.

Referring now to the drawing, and in particular to Figure l thereof, itwill be seen that numeral 1t) designates a front drive axle enclosedwithin a tubular housing 412. The outer 'end of the drive axle in theparticular form illustrated is provided with an external splined section14 While the other or inner end, not shown, is journale'd for relationwithin suitable bearings of well known design and is connected into auniversal joint which permits both rotational and pivotal movementthereof sov thatfthe wheels of Athe vehicle may be turned as `well asroll along the ground. A' second axle, also not shown, connects theuniversal into the differential in accordance with conventionalpractice. The differential is, in turn, connected into a transfer casewhich is operatively coupled with the vehicle engine byfmeans of atransmission that functions vto rotate the front and rear wheels at thesame speed when in four-wheel drive rotation. The transfer case formsthe means by which the front axles are disconnected from the engine andtransmission thus affecting a change from four to two-wheel driverelation and visa versa.

The wheel hub 16 is journaled for rotation on roller bearings 18 carriedon the end of the axle housing `12. A drive flange Z containing acentral opening 22 is attached to the outer end of the wheel hub in amanner which will be explained later. The splined section 14 on theouter end of the axle is provided with the rst interlocking means of thehub which, in the specific form illustrated, comprises a tubular element24 mounted thereon for conjoint rotation and containing a plurality ofangularly spaced longitudinal grooves sized and arranged to receive andlock over the splines. The inner section 26 of the tubular element has acylindrical outer surface that is journaled for rotation withinself-lubricated bushing 28 carried with a press t inside opening 22 ofthe drive flange against annular shoulder 30 formed on one side thereof.The'bushing is held in place by locking ring 32 on the inner end of thetubular element. With reference now to Figures l and 3, it will be seenthat the outer section of the tubular element 24 contains an integrallyformed annular flange 34 having one or more notches 36 cut into theperipheral edge thereof. In the preferred embodiment of the invention,ange 34 is provided with a plurality of notches 36 arranged inequiangularly spaced relation, four of which have been illustratedlocated 90 apart. Also, the under lines of the notches extend radiallyand the sides of each notch lie in spaced parallel relation on oppositesides of the under line thereof.

In Figures l, 2 and 3 it can be `seen that a face plate 38 covers theouter end of the drive flange 20 and is attached thereto by screws 40.The face plate and drive flange are, in turn, attached to the wheel hub16 for conjoint Vrotation by bolts 42. The drive ange 20, in effect,forms a housing within which the tubular element 24 rotates when the hubis set for two-wheel drive and to which said tubular element isoperatively connected for conjoint rotation with the hub in four-wheeldrive rotation. The drive flange also houses the second interlockingmeans that moves radially between engaged and disengaged positions withthe iirst interlocking means in a manner which will now be described.

Referring specifically to Figures 1, 3 and 4, it will be noted that theouter face 44 of the vdrive flange 20 contains a circular annular grooveor track 46 intersected at angularly spaced points by radial slots 48communicating central opening 22. These slots are preferably of the samewidth as the notches 36 in the tubular members and arranged in the sameequi-angularly spaced relation so that they will become alignedtherewith in selected relative rotational positions. In the formillustrated, slots 48 also open through the peripheral edge of the driveflange where they are covered by a ring I50` of greater width than thedepth of the slots to provide a grease-tight seal along the edges whichoverlap the ange and face plate. The slots are of greater depth than theannular groove 46 as is shown most clearly in Figure 4.

The second interlocking means comprises a pawl 52 mounted with afree-sliding fit for radial movement within each slot 48. Spring means54, shown in the form of coiled compression springs, are mounted in eachslot between the ring 50 and pawl urging the inner end thereof againstthe periphery of flange 34 of the tubular member which contains thenotches 36, thus, pawls 52 automatical- 1y snap into notches 36 underthe action of the com- Y 4 with the notches due to relative rotationalmovement betweeri'the drive flange and'axle or tubular element'unlessheld in disengaged position by the cams `56 which will be describedpresently.

Several important features are worthy of note at this point with regardto the manner in which the pawls become engaged n the notches of thetubular element even though not aligned therewith if the cam isinoperative to hold the pawls in disengaged position. First of all, withthe transfer case actuated in a manner to place the vehicle infour-wheel drive, it is assumed that the front and rear axles willrotate at exactly the same speed. It is seldom true, however, that theVfront wheels will rotate at exactly the Vsame speed as the rear wheelsdue to small differences in diameter of the tires caused by unequaltread wear. As a result, there will be a small amount of relativerotation between the drive axle and tubular element coupled thereto withrespect to the front wheel, drive flange, slots and pawls even instraight line driving. Thus, the pawls will rotate either slower orfaster. than the notches until they come into alignment therewith atwhich time interlocking engagement therebetween to form a Vdrivingconnection will take place. Even assuming the relatively rare situationin which the front axle and wheel are rotating at exactlythe same speedduring straight 'line driving so that there is no relative motiontherebetween, as soon as the front wheels are turned, the wheel on theinside of the turn runs slower and the outside wheel faster than theunloaded front axles causing almost immediate engagement of the pawls inthe notches. Also, as soon as one wheel becomes engaged, its drive axlewill act through the differential to produce relative rotary motionbetween the other front wheel and its axle until the pawls and nochesare aligned for the driving connection. It is important to note in thisconnection that both the front wheels and axles are turning the samedirection and at almost the same speed when in four-wheel drive whichmeans that the relative rotary motion therebetween is very slight thusallowing the pawls to slip easily into place.

If, on the other hand, the front drive axles are disconnected at thetransfer case to place the vehicle in twowheel drive and the cams aremoved to a position where the pawls are free to engage, the rst fewinches of movevment of the front wheels over the ground will produce therequired relative movement to ali-gn the pawls and notches. Of course,in the four pawl and notch conpawls engage. Obviously, insuiiicientspeed could be attained in this Ishort distance to damage the pawls asthey pass over the notches.

As a practical matter, of course, there is always relative motionbetween the front axles and wheels when disengaged even in straight linedriving which causes almost immediate alignment of the pawls andnotches. In certain rare situations it is possible, however, to producea high degree of relative motion between the front axles and disengagedfront wheels when the pawls are free to engage. This could occur byskidding the rear wheels rapidly on gravel or ice with the vehicle infour-wheel drive. It has been found, however, that the pawls do notbreak; but rather, they begin to chatter and do not fall into thenotches until the relative motion is reduced.

Finally, it will be seen that with the pawls engaged within the notches,the pawls are subjected to simple shearing stresses that they are easilyable to withstand without failure. The parallel sides of the pawls andnotches extending in spaced parallel relation to radial center linesproduce substantially no forces tending to back the pawls out of thenotches.

With reference now to all the figures of the drawing, it will be seenthat face plate 38 contains a central opening bounded by an annular ange58. The cani operator tioned to move into cup-like depressions 72 in theperiphery of the lock control corresponding to the engaged anddisengaged positions of the cams 56. The cam operator or lock controlalso includes an arcuate slot 74 arranged to receive pin 76 in the faceplate that functions to limit the relative rotational movement of thelock control between engaged and disengaged positions of the cam. Fingerholds 78 are provided in the face of the lock control along withmarkings 80 indicating the position of ,the cam.

Again with reference to Figures 1, 3 and 4, it will be noted that eachpawl 52 contains a slot S2 arranged to align with the annular groove 46in the drive flange when the pawls are in the retracted position inwhich' they cannot engage `within the notches 36 of the tubular element.The cams 56 comprise generally wedge-shaped projections on the insideface of the lock control which move arcuately within the annular trackin the drive ange. Opposed cam surfaces 84 and 86 on the cams and pawlsbordering the notches therein cooperate to retract the pawls when thelock control is rotated to move the cams from the dotted line positionof Figure 3 to the full line position. With the cam operator or lockcontrol retained in disengaged position by the ball detent 70, thesprings 54 are, of course, compressed between the retracted pawls andring 50. The pawlsV are freed for engagement by rotating the lock`control clockwise in Figure 2 until the arrow lines up with the index atthe In position which places the cams in the dotte line position ofFigure 3.

Having thus described the several useful and novel features of theselective drive hub of the present invention, it will be' seen that themany useful objects for which it was designed have been achieved.Althoughbut one specific embodiment of the invention has beenillustrated and described,.we realize that Vcertain changesandmodications therein many occur to those skilled in the art within thebroad teaching found herein; hence, it is our intention that the scopeof protection afforded hereby shall be limited only insofar as saidlimitations are expressly set forth in the appended claims.

What is claimed is:

1. A selective drive hub for eecting a driving connection between an endof a power shaft and a wheel hub` wherein the hub encircles and isrotatably mounted on the shaftand the shaft has an end portion extendingbeyond an end of the hub, comprising: disk-like means forming a driveflange having an inner face adapted to be secured to said end of the huband provided with a central opening therein through which the endportion of the shaft projects, the outer face of said disk meansincluding at least one radial slot and a cam-receivingtion with thecam-receiving recess of the disk means;V

spring means operatively connected to each pawl means urging the sameinto extended position; tubular means attached to the end portion of theshaft for conjoint rotation therewith, said tubular means including atleast one radial notch on the outside surface thereof sized and locatedto receive the pawl means in extended position when placed in radialalignment therewith by relative rotational movement between the powershaft and wheel hub; and, cam means mounted for sliding movement in `thecam-receiving recess of the plate-like means between an operative and aninoperative position, said cam means including cam surface adapted toengage the shoulder of the pawl means when moved from the inoperative tothe operative position to effect retraction of said pawl means againstthe action of the spring means thus releasing the driving connectionbetween the power shaft and wheel hub.

2. The invention according to claim l, wherein the disk-like meansincludes a plurality of radial slots arranged in equi-angularly spacedrelation and the tubular means is provided with one radial notch foreach slot arranged in the same spaced relation.

3. The invention according to claim l, wherein the sides of each slotand notch are arranged in spaced substantially parallel relationequidistant on opposite sides of a radial center line.

4. The invention according to claim l, wherein means are provided forreleasably locking the cam means in inoperative and operative positions.

5. The invention according to claim l, wherein the cam-receiving recesscomprisesan arcuate groove disposed concentrically about the axis of thepower shaft.

6. The invention according to claim 1, wherein the shoulder of the pawlmeans is formed by a transverse .slot therein located in alignment withthe cam-receiving recess when said pawl means is in retracted position.

7. The invention according to claim l, wherein a face plate having acentral opening therein is attached to the interface of the disk-likemeans, and the cam means comprises a cylindrical member mounted forrotation within the central opening of the face plate, said cylindricalmember including a cam projecting from the inner end thereof into thecam-receiving recess.

8. The invention according to claim 2, wherein the cam-receiving recesscomprises an arcuate slot disposed in Vconcentric relation about theaxis of the power shaft.

9. The invention according to claim 2, wherein the cam-receivingrecesscomprises an annular track arranged concentrically about the axis of thepower shaft, a face plate having a central opening therein is attachedto the outer face of the disk-like means, and the cam means comprises a`cylindrical member mounted for rotation within the central opening inthe face plate, said member having cams projecting into the annulartrack for. movement upon rotation of said cylindrical member intocontact with the shoulder of each pawl means to accomplish simultaneousretraction thereof.

l0. The invention according to claim `2, wherein the sides of each slot,notch and pawl means lie in spaced substantially parallel relation onopposite sides of a radial center line. t

l1. The invention according to claim 2, wherein the shoulder of eachpawl means is inclined to provide a cam surface positioned to engage onoppositely inclinedcam vsurface on each cam means when said cam means ismoved into operative position.

References Cited in the le of this patent UNITED STATES PATENTS 209,712Pratt Nov. 5, 1878 283,459 Bapple Aug. 21, 1883 449,383 Rathbun Mar. 3l,1891 831,745 Rice Sept. 25, 1906 y 865,302 Hanson Sept. 3, 19071,765,695 Owens ---l June 24, 1930Y 2,647,600 Anderson Aug. 4, 19532,727,402 Opocensky Dec. 20, 1955

